1. Field of the Invention
The present invention relates to a solid-state imaging device, and particularly to a solid-state imaging device used for a digital video camera and a digital still camera.
2. Description of the Related Art
In a solid-state imaging device used for a digital still camera or the like, there has been a tendency that the number of pixels is increased, while size of a pixel is reduced. Accordingly, the area of a photoelectric conversion unit is reduced, thereby reducing light receiving sensitivity. Further, the aspect ratio (depth/width) of a pixel structure is increased. The F-number of an on-chip lens is also increased. This reduces condensing efficiency, and light leaks to adjacent pixels, thereby causing crosstalk.
Conventionally, a solid-state imaging device including light guides as described in Japanese Patent Application Laid-Open No. H06-224398 has been proposed as a solution to these problems. The solid-state imaging device including the light guide according to the conventional art will hereinafter be described using a figure. FIG. 12 illustrates a schematic sectional view of a pixel unit of a solid-state imaging device of the conventional art. The solid-state imaging device of the conventional art includes a plurality of pixel units 200 arranged in a matrix manner. The pixel unit 200 includes a silicon substrate 201, a photoelectric conversion unit 202 disposed inside of the silicon substrate 201, and an inter-layer insulation unit 205 formed from transparent material on the silicon substrate 201. Wiring unit 206 is formed inside of the inter-layer insulation unit 205 at a predetermined position above the silicon substrate 201.
A high refractive index unit 203 is embedded inside of the inter-layer insulation unit 205 above each photoelectric conversion unit 202. The high refractive index unit 203 has a refractive index higher than that of the inter-layer insulation unit 205. The high refractive index unit 203 thereby configures a light guide. A taper unit is disposed above the light guide. The width of the taper unit gradually becomes wider toward the optical incident unit 204. Since the solid-state imaging device having such a configuration is adopted, light incident on the optical incident unit 204 is propagated while being concentrated in the high refractive index unit 203. As a result, the light is guided efficiently, while crosstalk is prevented from occurring above the silicon substrate 201.